Outer surface sheet for absorbent articles that include barrier flaps

ABSTRACT

An outer surface sheet ( 1 ) for absorbent articles, such as diapers, incontinence protectors or sanitary napkins, and comprises at least one upstanding barrier flap ( 5, 6 ) which extends across at least a part of the surface sheet. The surface sheet includes at least two parts ( 7, 8, 9 ) which are disposed to that bordering edge portions overlap each other. The barrier flap ( 5, 6 ) is comprised of a strip of elastic material that has two long edge portions and two end edge portions, wherein one of the long edge portions of said strip is inserted in a stretched state between the mutually overlapping edge portions of the two surface sheet parts ( 7, 8  and  7, 9  respectively) and firmly secured there-between.

FIELD OF INVENTION

The present invention relates to an outer surface sheet for absorbentarticles, such as diapers, incontinence protectors or sanitary napkins,comprising a central part and two side parts of inelastic materials,each of said parts having two longitudinal edge portions and adjacentlongitudinal edge portions of the central part and the respective sidepart are mutually overlapping each other; and further comprising abarrier flap extending along at least a part of each of the longitudinaledge portions of the central part

BACKGROUND OF THE INVENTION

The outer surface sheets of absorbent articles of the aforementionedkind will often include so-called barrier flaps on that side of thearticle which lies proximal to the wearer's body in use. The primepurpose of the barrier flaps is to prevent liquid from running over theupper side of the surface sheet and out to the edges of the absorbentarticle. The flaps also form together with the surface sheet abasin-shaped cavity in which discharged liquid is stored temporarilybefore the absorbent body has been able to absorb the liquid discharged.This temporary storage space is particularly important with regard toincontinence protectors for adult persons, since the volume of liquidthat is discharged onto such a product at one and the same time can berelatively large. In order to ensure that the liquid stored temporarilyin this storage space will not leak from the article, it is necessaryfor the barrier flaps to lie sealingly against the body of the personwearing an absorbent article that includes barrier flaps on its outersurface sheet. Barrier flaps are often comprised of elongated pieces ofinelastic material that are made elastic along one longitudinal edgepart with the aid of pretensioned elastic threads. Such flaps arefastened to the outer surface sheet with the elastic threads in astretched state. When these elastic threads are then allowed to relax,the flaps will take an upstanding position relative to the plane of thesurface sheet. One problem with flaps of this nature is that theinelastic material in the flaps will pucker as the elastic threadscontract. This puckering, or gathering, of the inelastic material meansthat the puckered longitudinal edges of the flaps will not sealeffectively against the wearer's body when an article that includes anouter surface sheet on which such flaps are provided is worn.

It is known from Applicant's Swedish Patent Application No. 9700694-4,filed Feb. 27, 1997, to produce barrier flaps from elastic band materialthat has a generally smooth abutment surface in both a stretched andrelaxed state. One problem encountered with the use of flaps comprisedof elastic material is the difficulty experienced in fastening the flapsto the outer surface sheet. This problem has been solved in theaforesaid Swedish Patent Application by using a three-ply film thatcomprises two polypropylene outer layers and an intermediate layer ofelastic film.

EP-A1-0 625 346 discloses a surface sheet according to the introductorypart of the description.

An object of the present invention is to provide an outer surface sheetfor absorbent articles that includes elastic barrier flaps which arefastened to the outer sheet in a manner such as to enable the use offlaps that consist solely of elastic material. Another object of theinvention is to provide such a surface sheet of flexible constructionthat can be produced in a cost-effective manner without complicating theprocess of manufacturing the absorbent articles in which the outersurface sheet shall be included.

SUMMARY OF THE INVENTION

These objects are achieved with an outer surface sheet according to theintroductory part of the description characterised in that the barrierflaps each is comprised of a strip of elastic material having two longedge portions and two end edge portions, wherein one of the long edgeportions of each of said strips is inserted between the overlappinglongitudinal edge portions of the coal part and respective side part andfirmly secured therebetween. Because the elastic barrier flaps arefastened between two inelastic materials, it is easy to produce a secureattachment of the barrier flaps, regardless of whether the flaps areglued or welded in place. Furthermore, the division of the outer surfacesheet into separate parts enables the outer sheet to be given a flexibleconstruction by virtue of the fact that the different parts of saidsheet may be comprised of different materials.

In one preferred embodiment of the invention, that longitudinal part ofthe strip which lies between the mutually overlapping longitudinal edgeparts of the surface sheet parts is fastened to each of said overlappingparts.

According to a more preferred embodiment of the invention, the surfacesheet parts are made of a heat-weldable material and the mutuallyoverlapping longitudinal edge parts of the surface sheet parts arejoined together by ultrasound welding or heat welding. The overlappingedge portions of the surface sheet parts are joined together through thelongitudinal edge part of the stretched elastic strip sandwichedtherebetween. The surface sheet will preferably comprise three separatelongitudinal parts, two side parts and a central part, wherein at leastthe central part will comprise a liquid permeable material, and abarrier flap will extend along the two long edges of said central part.In one variant, the two side parts of the surface sheet are comprised ofliquid impervious material and the mutually overlapping longitudinaledge portions of the side parts are placed on top of respectivelongitudinal edge portions of the central part. Each barrier flap ispreferably comprised of a strip of elastic plastic film and tapers ornarrows in a direction towards its end parts. Alternatively, the barrierflaps may taper from their end parts towards their centre part.

In one variant, at least one barrier flap extends in the transversaldirection of the outer surface sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in more detail withreference to exemplifying embodiments thereof and also with reference tothe accompanying drawings, in which

FIG. 1 is a schematic perspective view, shown obliquely from above, ofan incontinence protector that includes an outer surface sheet accordingto the invention;

FIG. 2 is a cross-sectional view taken on the line II—II in FIG. 1;

FIG. 3 is a cross-sectional view illustrating a first method ofproducing an inventive outer surface sheet; and

FIGS. 4 and 5 are respective cross-sectional views illustrating a secondmethod of producing an inventive outer surface sheet.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIGS. 1 and 2 illustrate an incontinence protector 1 for personssuffering from light incontinence. The incontinence protector 1typically includes an absorbent body or core 2 which is sandwichedbetween a liquid-permeable outer surface sheet 3 and aliquid-impermeable outer backing sheet 4. The sheets 3 and 4 aremutually joined along sheet parts that lie outside the absorbent body 2.The incontinence protector 1 also includes two longitudinally extendingbarrier flaps 5, 6 which extend along the full length of the article inspaced relationship with the longitudinal edges of the absorbent body.

According to the invention, the liquid-permeable surface sheet 3 iscomprised of a central part 7 and two side parts 8, 9. The longitudinaledge portions of the side parts 8, 9 that border on the central part 7are disposed so as to overlap respective longitudinal edges of saidcentral part 7. One of the longitudinal edge portions of the barrierflaps 5, 6 is disposed between the mutually overlapping longitudinaledge portions of the central part 7 and respective side parts 8, 9 andthe mutually overlapping longitudinal edge portions of the central part7, the side parts 8, 9 and the barrier flaps 5, 6 are glued or weldedtogether.

The incontinence protector 1 also includes leg elastic in the form oftwo elastic strips 10, 11 that are fastened between the outer sheets 3,4—as will be best seen from FIG. 2.

In the illustrated embodiment, the absorbent body 1 is comprised ofcellulose fluff either with or without an admixture of so-calledsuperabsorbent particles. However, the absorbent body may comprise anymaterial, or materials, used in absorbent bodies for absorbent articlesof the kind mentioned in the introduction. The absorbent body mayalternatively be comprised of more than one layer of absorbent material,and may even include layers of wadding or like material so as to quicklyremove discharged liquid from the liquid receiving outer surface sheet.

The liquid impermeable sheet will preferably be made of plastic film,for example polyethylene film, although all other materials used asliquid impermeable sheet material for absorbent articles may, of course,be used.

The central part 7 of the liquid impermeable outer surface sheet 3 willpreferably consist of perforated plastic film or nonwoven material,although it will be understood that any material used for producingliquid permeable outer sheets for absorbent articles of the aforesaidkind may, of course, be used. The side parts 8, 9 may consist of thesame material as the central part 7, although said side parts 8, 9 willpreferably be comprised of a liquid impermeable material. In this lattercase, these side parts will then function as edge seals and enhancesafety against side edge leakage.

The barrier flaps are made of an elastic material, for example elasticfilm. The elastic material used in the barrier flaps may be based onstyrene block copolymers, such as styrene-butadiene-styrene (SBS),styrene-isoprene-styrene (SIS), styrene-ethene-butene-styrene (SEBS) orstyrene-ethene-propene-styrene (SEPS). The elastic material may alsocomprise several layers, provided that the layer material will notpucker as the material contracts or relaxes.

It is normally difficult to weld elastic film to inelastic material,owing to the different melting points of the different polymers includedin the materials. Problems are also experienced when gluing elastic filmto inelastic material, due to the shear forces occurring in the join.These difficulties are overcome in accordance with the invention, bysandwiching the attachment part of the elastic material between twolayers of inelastic material. This enables the two layers of inelasticmaterial to be spot-welded to one another, through the elastic material.Distribution of the stresses in the glue joints is also enhanced in thatcase when the elastic material is glued to both inelastic materiallayers between which the elastic material is inserted.

Because the barrier layers are fastened to two layers of inelasticmaterial, that part of the outer surface sheet located within the joinregions of the barrier flaps will be stiffer than the remainder of thesheet. This reduces the risk of the outer surface sheet puckering whenthe elastic barrier flaps contract subsequent to manufacture of thedescribed incontinence protector.

Fastening of the barrier flaps between two layers of inelastic materialas described above provides a wide choice of material from which thebarrier flaps can be made, since it is not necessary to take theweldability of the flaps to other materials in the outer surface sheetinto account when choosing said material. The inventive fasteningprinciple may, of course, also be applied with barrier flaps that arenot fully elastic, for example conventional barrier flaps having freeedge parts that have been made elastic with the aid of prestretchedelastic threads, or barrier flaps made of elastic shrink film.

FIG. 3 illustrates schematically a method of manufacturing the outersurface sheet 3 shown in FIGS. 1 and 2. The sheet 3 is manufacturedsimply by laying prestretched, elongated strips or bands 12, 13 on afirst web 14 of heat-weldable, liquid-permeable material, such that theouter edges of the strips or bands 12, 13 and the material web 14 willlie edge to edge. Elongated second webs 15, 16 of heat-weldable materialare then applied, so that the inner long-edge portions of the secondwebs 15, 16 overlap the long edge portions of the strips 12, 13 and thefirst web 14. The mutually overlapping portions of the first web 14, thestrips 12, 13 and the second webs 15, 16 are then passed through the nipdefined between an ultrasound horn of an ultrasound welding unit and ananvil means, as indicated schematically by arrows in FIG. 3, therewithjoining these components together.

The described method of manufacture is well suited to the continuousmanufacture of the outer surface sheets of absorbent articles providedwith barrier flaps. For instance, outer surface sheets can beprefabricated and then reeled up onto storage reels which can be placedin position in a production line for the manufacture of absorbentarticles, such as incontinence protectors, for instance. The manufactureof outer surface sheets provided with barrier flaps may alternativelytake place in the production line and said surface sheet introduced intothe production line immediately the mutually overlapping portions of thefirst material web, the elastic strips and the second material webs havebeen joined together in the manner described. A thus produced outersurface sheet is, for instance, placed on a web of liquid impermeablematerial subsequent to having placed a line of absorbent bodies on saidmaterial.

The last manufacturing stage in such an incontinence protectorproduction line comprises cutting separate incontinence protectors fromthe continuous composite web of outer sheets and intermediate absorbentbodies. Subsequent to having cut individual incontinence protectors fromthe production line, the barrier flaps, which have been kept stretchedduring the entire manufacturing process, can be allowed to relax andtherewith take a position in which they are upstanding relative to theliquid-permeable outer surface sheet, as shown in FIGS. 1 and 2.

FIGS. 4 and 5 illustrate another method of manufacturing an outersurface sheet in accordance with the invention. As in the earlierdescribed method, two prestretched strips 12′, 13′ are placed on top ofa web 14′ of liquid-permeable and heat-weldable material. In thisembodiment, however, the strips 12′, 13′ are spaced slightly from therespective side edges of the web 14′. Those portions 15′, 16′ of the web14′ that lie outside the outer extremities of the strips 12′, 13′ arethen folded in over said strips 12′, 13′ and the central part of the web14′, in the manner shown in FIG. 4, whereafter the outer edge portionsof the strips 12′, 13′ are welded to the outer edge portions of thecentral part of the web 14′ and to the outer edge portions of theinwardly folded parts 15′, 16′ of the web 14′, as indicated by arrows inFIG. 4. The web portions 15′, 16′ are then folded back, as shown in FIG.5. FIG. 5 shows the manufactured outer surface sheet with barrier flaps12′, 13′ in its contracted state.

It will be understood that the aforedescribed embodiments of an outersurface sheet may be modified within the scope of the invention. Forinstance, the barrier flaps need not extend along the full length of thesurface sheet. Neither need the free long edge portions of the barrierflaps extend rectilinearly, but may, in principle, have any shapewhatsoever, for instance the height of the barrier flaps may be shorterat the end parts of the surface sheet than in its longitudinal centrepart. The strips or bands forming the barrier flaps may be configured sothat they will exhibit curved fastener parts when stretched, whilegiving the long-edge portions of the central part of the surface sheetand its side parts a corresponding curvature. Although the describedembodiments include solely barrier flaps that extend in the longitudinaldirection of the outer surface sheet it will be understood, of course,that barrier flaps that extend transversely of the outer sheet may alsobe included. The invention is therefore only restricted by the contentsof the accompanying claims.

What is claimed is:
 1. An outer surface sheet for absorbent articles(1), comprising a central part (7) and two side parts (8,9) of inelasticmaterials, each of said parts having two longitudinal edge portions andadjacent longitudinal edge portions of the central part (7) and therespective side part (8,9) are mutually overlapping each other, andfurther comprising a barrier flap (5,6) extending along at least apartof each of the longitudinal edge portions of the central part,characterised in that the barrier flaps (5,6) each is comprised of astrip of elastic material having two long edge portions and two end edgeportions, wherein one of the long edge portions of each of said stripsis inserted in a stretched state between the overlapping longitudinaledge portions of the central part (7) and respective side part (8,9) andfirmly secured therebetween.
 2. A surface sheet according to claim 1,characterised in the long edge portion of each strip (5,6) locatedbetween the respective overlapping longitudinal edge portions of thecentral part (7) and the respective side part (8,9) is fastened to bothof said overlapping longitudinal edge portions.
 3. A surface sheetaccording to claim 1, characterised in that the central part (7) and theside parts (8,9) of the surface sheet are comprised of heat-weldablematerial; and in that the mutually overlapping longitudinal edgeportions of the central part (7) and the respective side part (8,9) arejoined together by ultrasound welding or heat welding.
 4. A surfacesheet according to claim 3, characterised in that the overlappinglongitudinal edge portions of the central part (7) and the side parts(8,9) are fastened together through the long edge portion of theprestretched elastic strip (5,6) located therebetween.
 5. A surfacesheet according to claim 1, characterised in that at least the centralpart (7) of the surface sheet (7, 8, 9) is comprised of a liquidpermeable material.
 6. A surface sheet according to claim 5,characterised in that the two side parts (8,9) of the surface sheet arecomprised of a liquid impermeable material.
 7. A surface sheet accordingto claim 1, characterised in that each barrier flap (5, 6) is comprisedof a strip of elastic plastic film.
 8. A surface sheet according toclaim 1, characterised in that the barrier flaps taper in a directiontowards their respective end edge portions.
 9. A surface sheet accordingto claim 1, characterised in that the barrier flaps taper from theirrespective end edge portions in towards their respective centreportions.
 10. A surface sheet according to claim 1, characterised inthat at least one barrier flap extends transversely across said surfacesheet.